Olfactophilia or osmolagnia is a paraphilia for, or sexual arousal by, smells and odors emanating from the body, especially the sexual areas. Sigmund Freud used the term osphresiolagnia in reference to pleasure caused by odors.
Odour is sensory stimulation of the olfactory membrane of the nose by a group of molecules. Research has shown that certain body odours are connected to human sexual attraction. Humans can make use of body odour subconsciously in order to identify whether a potential mate will pass on favourable traits to their offspring. This is based on the fact body odour may provide significant cues about the genetic quality, health and reproductive success of a potential mate. There is an extensive amount of research demonstrating that body odour affects sexual attraction in a number of ways including through human biology, the menstrual cycle and fluctuating asymmetry. Research indicates that body odour also affects the sexual attraction of insects and mammals.
Research has attempted to understand the relationship between various aspects of human biology and genetics with sexual attraction. This includes the role of the major histocompatibility complex (MHC), the human leukocyte antigen (HLA) and their different heterozygotic variations. While research is not conclusive, hypotheses suggest such genetic factors play a role in sexual selection. Signalling odours in reproduction are referred to as attractants, and aim to bring about successful mating by both males and females. Although there is no universally accepted understanding of how and why odours differ from each other, neurophysiological studies have advanced our knowledge.